The Study On The Application Of Evenness Control System In The Nonwoven Dry Process

Evenness is an important property index of the nonwoven product quality,which has a direct impact on product performance and the subsequent processing of end-use performance.Evenness control system is an important means to control about the product evenness,but such technology in China is still far behind the foreign countries.The further study on envenness control system is helpful to guide Chinese enterprises fully understand and use the technology,helpful to develop and innovate Chinese system.In order to understand advanced uniformity control system,the subject focuses on the following three aspects by means of combination of mathematical analysis and experimental with large amount of literature queries and practice in the factory:Firstly,study on the theory of web evenness control system by observing the speed change of doffers and carriages of the cross-lapper to show the relationships between speed change and the evenness curve.Secondly,research on the influence on the product quality when using the evenness control system,including the evenness curve settings,the role of the system automatically feedback function,the matching situation between the automatic detection and the actual product uniformity,the influence on the product evenness and the breaking strength with different process parameters and observing and analyzing the distribution of the evenness by MATLAB;Thirdly,build the optimal model which is in line with the actual production process in the factory.From the research mentioned above,the solution is as follows:Delay time has a great impact on the evenness control in the MD direciton while the evenness curve control the evenness in the CD direction.The evenness in the CD direction improves with evenness curve and the producing rate increases 3.5%.Evenness control system is not suitable to all kinds of processes.It has a less important role in the low density,but has a better important role in the high density.The actual distribution of evenness is the same as the trends of screen of automatic detection in the line.But the ratio of raw materials will have an impact on the automatic detection results about the density of products,the more 10%polyester in the raw material,the more 1g/m² in the density of product.With the density decreasing,the strong in CD and MD increases,the ratio of CD/MD decreases and bonding index increases rapidly when the density is lower than 100g/m²,and decrease rapidly when the density is higher than 100g/m².At last,product evenness will be stabilizing.When the fold is 4 and above,CV can be controlled within 1～1.5%, with the draft ratio 2.5.Factors influencing values of CV are drafting ration,folds number and density in turn.From the optimal design,web can be detected totally when folds number,f,meets f≥ν_a/ν_CD.The optimal parameters can be got by optimal models as follows,the output speed of NO.1 card machine is 104m/min, the output density is 30.6 g/m²,and the width is 2.8m;the folds number is 6 and the output width is 3.8m;the draft ratio is 1.554;the output density of NO.2 card machine is 36.7 g/m².Finally,the product is 672kg/h with the value of CV less than 1.1%.